1. Field of the Invention
This invention relates to a stamp unit, and particularly to a stamp unit whose print face portion is formed of a heat sensitive stencil paper in place of rubber.
2. Description of the Related Art
There has been conventionally utilized various kinds of stamps each of which serves to print a company name, an address or other character arrays on the surface of a sheet and has a print face portion formed of rubber.
Usually, this type of stamp is individually made to order. Hence, they are expensive and a user must wait for a long time to receive them from an order.
On the other hand, a heat sensitive stencil paper has been conventionally used for printing in which a desired pattern can be perforated by irradiation of infrared rays or a thermal head, and ink is transmitted through a perforation array to print various kinds of patterns of character arrays, figures, marks or the like.
In U.S. Pat. No. 5,285,725, the applicant of the present application proposed a stencil plate that mainly contains a heat sensitive stencil paper as described above and an impregnation member impregnated with ink. The stencil plate is suitable to prepare a stamp in place of the conventional stamp having the print face portion formed of rubber as described above.
The stencil plate is formed as follows. An impregnation member impregnated with ink and a frame member surrounding the impregnation member are adhesively attached to a synthetic resin film, and a heat sensitive stencil paper is adhesively attached onto the surfaces of the impregnation member and the frame member.
When the stencil plate as described above is applied to a stamp, the stencil plate is adhesively attached to the lower surface of the base portion of a stamp member having a grip portion through a cushion member, and a desired pattern of a character array or the like is perforated on a heat sensitive paper by irradiation of infrared rays or a thermal head. With this construction, a stamp that comprises a stamp member and a stencil plate and can print the desired character-array pattern or the like on sheets over many times can be obtained.
In a stamp to which the heat sensitive stencil paper as described above is applied, the heat sensitive stencil paper located on the lower surface of the impregnation member constitutes the print face portion. A frame having a width is provided around the print face portion, and thus, it may suffer from a number of problems. In particular, it is difficult to locate the print face portion at a desired position on the surface of a sheet for a printing operation; the ink leaks from the print face portion due to its weight when the stamp is left erect during periods of nonuse; and the print face portion is damaged or dust collects on the print face portion because no protection member for protecting the print face portion is provided, and print performance is liable to be reduced.
Further, the above stamp is designed so that the heat sensitive stencil plate is provided on the lower surface of a base portion of a stamp member having a grip member through a cushion member. Therefore, when an impregnation member fixed to the stamp member lacks ink, a new stamp unit must be used. Accordingly, each stamp unit is required to be disposable, which increases costs. Further, if the stamp unit is designed to exchange a frame portion to which a new impregnation member impregnated with ink adheres, it is difficult to secure a portion to be detached for exchange. Therefore, for exchange, not only the hands are stained, but also peripheral portions are also stained. In addition, there is a possibility that ink is excessively supplied when the stamp is used.